Bulding a zone

Although farmers can't agree on the best tools to use for strip till, they do agree that the practice produces benefits for corn.

Strip tillage could be the fastest growing conservation tillage system in the nation, but then nobody is actually counting. In fact, no definition of the practice exists and there are as many different ways to strip till as there are farmers adopting it. Even the Conservation Technology Information Center has trouble categorizing the practice, lumping it with other tillage systems and suggesting that "popular strip-tillage and zone tillage are not official survey categories but rather modifications of no-till, or other tillage types." Michigan farmer and zone-till innovator Ray Rawson likes to call it "organized tillage."

Proponents do agree, however, that the appeal of strip tillage lies in its ability to mix the high-residue advantages of no-till with the soil warming and germination benefits of conventional tillage. Many companies now sell strip-tillage units, making it easier to get started, but farmer innovations still abound.

"Corn is not well adapted to no-till systems," says Jim Kinsella, the farmer-innovator who heads the Ag Technology Center in Lexington, IL. "Heavy crop residue can have detrimental effects on no-till corn and it will tie up your nitrogen," Kinsella explains. "Strip tillage gets around those problems." Kinsella should know. He's been no-tilling his own 650 acres of corn and soybeans since 1975 and now believes he's found the proper balance of conservation and cropping system to maximize corn production.

No hard-and-fast rules. A field qualifies as a no-till operation if no more than 25% of the row residue is disturbed when making strips. Kinsella works a small 4-in. tillage strip within his 36-in. corn rows. Down the road in Shirley, IL, however, committed no-till/strip tiller Terry Schneider makes a 9-in. swath for his 30-in. rows. But strip width is only the first of many variations found among strip-tillage programs.

A basic strip-till unit consists of three pieces of equipment mounted on a toolbar, with the number of strip-making units matched to corn planter rows. Differences still arise, however, with the way each operator assembles and uses these basic pieces.

1. Single, front discs positioned to cut through residue. Kinsella recommends using discs at least 20 in. across, which he says helps reduce the amount of residue that gets caught in the equipment. Others say 18-in. discs work adequately.

2. Knives that lift without cutting additional channels into the soil. The biggest mistake a grower can make, Kinsella cautions, is using nitrogen applicator knives and calling it strip tillage. This practice caused such severe erosion and water-quality problems in Iowa last spring, he says, that state regulators threatened a ban on fall stripping. Kinsella endorses the mole knife, manufactured by Hi-Pro Mfg., Watseka, IL, that incorporates a flat plate welded to the bottom, augmenting soil lift. These should run between 7 to 9 in. deep.

Rawson's zone-builder unit uses larger knives that run much deeper, a practice he insists is necessary at least for first-time stripping. "You've got to do the deep tillage first and open up those channels for root penetration," he explains. "Then the next year you can come in and run the knives shallower." Although Rawson's knives resemble subsoiler units, he says they don't fracture the ground but gently lift soil into small waves.

3. Disc sealers to mound soil into strips. Discs should throw residue on top of mounds, without cutting additional channels into the soil. Rawson prefers two offset, fluted coulters, whereas Kinsella advocates a pair of unsharpened, concave discs, angled to heap soil onto the strip. The more residue mounded in the strip the better, according to Kinsella. "Mounds must survive winter freezing, thawing and blowing, and you can't make them too high," he asserts. "Winter, earthworms and microbial action will take care of most of the residue."

Strip tiller Cliff Roberts of Kentland, IN, takes issue with that statement, however, noting that driving on top of highly mounded strips with a planter isn't easy. Other strip tillers agree that the greatest challenge they face is accurately navigating their strip at planting. Advanced technologies could solve this problem with a guidance system that senses direction from strip tops, but development costs make this solution unlikely any time soon. Rawson doesn't worry if his planting doesn't always match his fall strips. "Nobody's perfect," he says, "and the roots will find their slot soon enough."

When is the best time? Kinsella also insists that fall strips are the only correct way to work the system, but other farmers are making early spring or even planting time tillage strips. "I'm gaining about 200 heat units a year in my strips, compared to straight no-till," Kinsella says. "I get more heat units and a lot less erosion this way. I can get planting into my strips quicker, in many cases. Then, I still have the residue between the rows to keep my crop cooler and drier during June, July and August." He also worries that spring strips are more conducive to erosion.

On the Schneider farm, because they're never sure how many acres of corn will go where, they count on early spring strips to precede planting. Meanwhile, zone-till innovator Ray Rawson suggests that mounting strip-tillage equipment directly on the planter still offers benefits over straight no-till. Southwest Iowa farmer Dave Kusel strives for a mixture of all three systems.

"Last fall's wet weather prevented us from making strips so this spring we started making strips again, but couldn't keep up. Our future goal is to get 30 to 50 percent of our acres done in the fall, 20 to 40 percent using spring row cleaning and the balance planted in true no-till with our 4-row John Deere mudder," relates Kusel. "We still like fall strips best, but this plan will help break up our workload and help us manage the sloping ground we have."

Strip-tillage fertility programs also differ widely among practitioners and, even for Kinsella and Rawson, remain a work in progress. Kusel's basic program includes N-serve-treated fall anhydrous applications, but he says, "The ultimate program may include small amounts of P, K and about 10 pounds of zinc."

Kusel worries that Iowa will ban fall anhydrous applications someday because of concern about nitrogen runoff. Kusel claims that a ban won't stop him from making fall strips without fertilizer, and he's questioning the need for starter fertilizer. "We know the crop looks better and seems to be taller and healthier in the spring when we use starter, but come fall, yields don't seem to be much different. We're still experimenting with our fertility programs."

Even though strip tillers argue the fine points of fertility management, strip height, width and depth and proper coulter selection, there's at least one thing they all agree on: Planting into strips gives corn growers a jump on the season.